Quadratus Lumborum

Original Editor - Vanessa Rhule

Top Contributors - Vanessa Rhule, Lucinda hampton, Kim Jackson, Ahmed Nasr, Joao Costa, George Prudden, WikiSysop, Wanda van Niekerk, Admin, Wendy Walker and Naomi O'Reilly

Introduction

The Quadratus Lumborum (QL) is the deepest back muscle and originates from the iliac crest and inserts on the transverse process of lumbar one through five and the lower part of the twelfth rib. The QL muscle is flattened and has a quadrangular shape.

The QL muscle is an integral part of the thoracolumbar fascia, a myofascial system that covers the posterior area of the human body, involving part of the lower and upper limbs.

Innervation of the QL is via the twelfth thoracic nerve and the spinal rami of the lumbar spinal nerves.

Along with the multifidus and erector spinae muscles, the QL helps to create an antagonist force to the muscles of the anterolateral abdomen wall.

Image: Quadratus lumborum (highlighted in green) - anterior view

Anatomy

Muscles of the Abdomen Posterior

The muscular organization is complex (comprises three layers with muscle fibers that have different vectors) and it is difficult to identify precisely the actions that occur through the contraction of fibers.

Generally, the QL muscle is located medially to the aponeurosis of the transverse abdominal muscle.

The quadratus lumborum (QL) muscle is:

• An integral part of the thoracolumbar fascia and also
• One of the muscles of the posterior abdominal wall.
• One of the Core Muscles
• One of the paraspinal muscles

Origin

Iliolumbar ligament and internal lip of Posterior iliac Crest.

Insertion

Medial half of lower border of 12th rib and tips of transverse processes of lumbar vertebrae.

Nerve Supply

• Subcostal nerve (T12)
• Iliohypogastric and Ilioinguinal nerve (both from L1)
• Branches from the ventral rami (L2 and L3)

Function

Quadratus lumborum visible

The anatomy texts describe the quadratus lumborum muscle as an extensor of the lumbar spine, a stabilizer of the lumbar area, capable of pelvic tilting laterally and capable of acting as an inspiratory accessory muscle.

However findings show

• During extension, the QL exerts a force of 10 N, compared to 100 N and 150 N of the erector spinae muscles and the multifidus. It seems unlikely that it can extend the lumbar area on a sagittal plane with such a small force (10 N).
• The QL during a lateral tilt of the trunk it participates with less than 10% of the force required for a coronal inclination.

It seems likely that QL could act as a crossroad of the forces exerted by the neighboring muscles, influencing the vectors of the different tensions produced, thanks to its :strategic position; disorganised scheme of its fibers; and its function in the myofascial system.

Actions

Classic described actions given below:

• Quadratus Lumborum fixes the 12th rib to stabilize diaphragm attachments during inspiration
• Lateral flexes the vertebral column
• Extends lumbar vertebrae
• It forms with the contralateral Tensor fascia lata and Gluteus medius a lateral myofascial sling which aims to maintain frontal plane stability of the pelvis.

Physiotherapy Implications

Quadratus lumborum trigger points

The muscle group is considered a postural muscle group and part of the Core muscles. The core is the group of trunk and hip muscles that surround the spine, abdominal viscera and hip. Core muscles are essential for proper load balance within the spine, pelvis, and kinetic chain. They spare the spine from excessive load and are essential for lad transfer between the upper and lower body.

Quadratus lumborum is a continuation of transverse abdominal muscle. The transverse abdominal muscle is part of the anterior fascial system of the body. The transversalis fascia penetrates the abdominal musculature. It's one of the muscles that tends to be tight and overactive In this situation adversly affects the resting tension of the QL, altering the distribution of the lumbar region load.

Trigger points can involve the QL. This condition could also mimic a painful syndrome of the lumbar area. Trigger Point Referral Pattern

For more see Quadratus Lumborum Syndrome

Lumbar spine pathologies eg bulging discs, and facet joint hypertrophy from chronic inflammation may effect nerve conduction and response to the QL and Iliopsoas resulting in poor muscle stabilisation and mechanical stress from chronic contracture.
QL can cause low back pain with the emergence of a heterotopic ossification or myositis ossificans. The latter may result from direct trauma and inadequate healing.